A multipath Transmission Control Protocol (TCP) has been proposed to increase the TCP throughput due to the diversity and also increase the reliability by opening multiple paths per TCP session in comparison with a conventional single path TCP. A representative use case of a MultiPath TCP (MPTCP) is data offloading applying the MPTCP to 3G/WiFi.
FIGS. 1A, 1B, and 1C illustrate a multipath Transmission Control Protocol (TCP) according to the related art.
Referring to FIGS. 1A to 1C, the MultiPath TCP (MPTCP) largely has two problems.
First, a random packet loss may occur. For example, as illustrated in FIG. 1A, when packets 4, 5, 6, 7, 8, and 9 are transmitted from a source 110 to a destination 120, packets 4, 6, 8, and 9 are transmitted through a first path 130 and the remaining packets 5 and 7 are transmitted through a second path 140. At this time, as illustrated in FIG. 1B, a packet loss may occur in the second path 140. Packets 5 and 7 to be transmitted through the second packet 140 may not be transmitted through the second path 140 but may be transmitted to the destination 120 through the first path 130. As described above, due to the packet loss which may occur in each path, out-of-ordered packets are generated and thus a TCP window size is reduced, thereby reducing the overall TCP throughput.
Next, an end-to-end delay variation may occur. The end-to-end delay refers to an amount of time spent while the packet is transmitted from the source to the destination. As illustrated in FIG. 1C, since respective paths have different path qualities in the multipath TCP, the end-to-end delay varies depending on the path. At this time, in the TCP, sequences of the received packets should be accurate. Accordingly, a request for reordering packets may be generated due to a difference of the delay according to the respective paths and thus a latency problem may happen. Further, since a User Equipment (UE) is required to wait for a packet from a poor quality path having a serious delay, the poor quality path may correspond to a bottleneck and the overall performance may be reduced.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.